Non-volatile memory has been widely applied in memory cards and USB flash drives. Since consumers demand for memory having higher access speed and accuracy but lower power consumption, it has now become an important issue as how to develop a memory with increased data access speed and accuracy to satisfy the market demands. Presently, in most cases, electronic engineers try to obtain increased memory access speed and accuracy by reducing the offset voltage of a current-sense amplifier for the memory. The offset voltage would adversely affect the quality of a circuit system. In a current-sense amplifier for memory, an input offset voltage thereof would cause unstable current detection accuracy to thereby reduce the memory data read speed and accordingly, result in incorrect data reading. In conventional solutions, the offset voltage of the current-sense amplifier is compensated in order to obtain increased current detection accuracy.
FIG. 1 is a circuit diagram of a conventional automatic offset compensation scheme with ping-pong control for complementary metal-oxide-semiconductor (CMOS) operational amplifier (data source: IEEE Journal of Solid-state Circuits, Vol. 29, No. 5, May 1994). As shown, the amplifier is electrically connected to a compensation circuit, which includes a current mirror and an adjustable transistor. The adjustable transistor controls the current gain of the current mirror, so as to adjust the offset compensation voltage. In the conventional automatic offset compensation scheme shown in FIG. 1, a control voltage VC is input to a gate of the adjustable transistor to control the working property of the adjustable transistor and accordingly, affect the current gain of the current mirror. The control voltage VC is obtained by converting an output voltage of the amplifier using a digital-to-analog converter (DAC). A computing circuit analyzes the effect of a previous offset compensation, in order to adjust the next compensation voltage. Thus, the control voltage VC is not a fixed voltage.
The conventional offset compensation circuit is mainly composed of transistors and capacitors, and feeds back the output voltage of the amplifier to compensate the offset voltage of the current-sense amplifier. However, due to the amplifier's circuit structure, the compensation effect is adversely affected and fails to achieve ideal compensation, which in turn hinders the memory from providing increased data read speed and accuracy. It is therefore tried by the inventor to work out a way for effectively reducing the input offset voltage of the current-sense amplifier in order to enable increased memory data access speed and accuracy.